Isolated Co single atoms in nitrogen-doped graphene for aluminum-sulfur batteries with enhanced kinetic response

Al-S batteries are promising next generation energy storage devices due to their high theoretical energy density (1340 Wh kg−1), low cost, and safe operation. However, the electrochemical performance of Al-S batteries suffers poor reversibility owing to slow kinetic processes determined by the difficulty of reversible conversion between Al and S. Here, we proposed a single-atom catalysts comprising Co atoms embedded in a nitrogen-doped graphene (CoNG) as an electrochemical catalyst in the sulfur cathode that renders a reduced discharge-charge voltage hysteresis and improved sulfur utilization in the cathode. The structural and electrochemical analyses suggest that the CoNG facilitated both the formation and oxidation of AlSx during the electrochemical reactions of the sulfur species. Consequently, the CoNG-S composite can deliver a considerably reduced voltage hysteresis of 0.76 V and a reversible specific capacity of 1631 mAh g−1 at 0.2 A g−1 with a sulfur utilization of more than 97%.